High-strength high-conductivity copper alloy

ABSTRACT

Disclosed is a copper alloy containing Fe of 0.01 to 0.5% and P of 0.01 to 0.3% in mass with the balance consisting of copper and unavoidable impurities, wherein the mass content ratio of Fe to P, namely Fe/P, is in the range from 0.5 to 6.0 and the volume fraction and the number of dispersoids of 1 to 20 nm in average particle diameter in the microstructure of the copper alloy are 1.0% or more and 300 pieces/μm 2  or more, respectively. The Cu—Fe—P alloy can secure a high strength and a high conductivity simultaneously.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a high-strength high-conductivity copper alloy, for example to a copper alloy suitable as a material for an IC lead frame used in a semiconductor device. A copper alloy according to the present invention is used in various fields but the present invention is hereunder explained on the basis of the case where the copper alloy is used for an IC lead frame which is a semiconductor component as a representative application.

2. Description of Related Art

As a copper alloy for an IC lead frame, a Cu—Fe—P alloy has heretofore been used generally. For example, a copper alloy containing Fe of 0.05 to 0.15% and P of 0.025 to 0.040% (C19210 alloy) or a copper alloy containing Fe of 2.1 to 2.6%, P of 0.015 to 0.15% and Zn of 0.05 to 0.20% (CDA194 alloy) is widely used as an international standard alloy since it is excellent in strength, electric conductivity and thermal conductivity among copper alloys.

In recent years, as a semiconductor device has been required to have a larger capacity, a smaller size and higher integration, the cross-sectional area of an IC lead frame is being reduced. With the trends, a copper alloy component used for an IC lead frame in a semiconductor device is required to have yet higher strength, electric conductivity and thermal conductivity. The situation is also applicable to a copper alloy used for not only IC lead frames but also other electric conductive components such as connectors, terminals, switches, relays, etc. in electric and electronic components.

An advantage of a Cu—Fe—P alloy is that it has a high electric conductivity and, in order to increase its strength, a means of increasing the contents of Fe and P or adding Sn, Mg, Ca or the like as a third element has so far been taken. However, the increase of the amount of such elements causes strength to be increased but an electric conductivity to deteriorate inevitably. Therefore, it has been difficult merely by controlling the chemical composition of a copper alloy to realize a Cu—Fe—P alloy having a good balance between a higher conductivity and a higher strength or simultaneously having both the properties which are required along with the aforementioned trends of a larger capacity, a smaller size and higher integration of a semiconductor device.

To cope with the difficulty, it has hitherto been proposed to control the microstructure or the precipitation state of dispersoids in a Cu—Fe—P alloy. For example, JP-A No. 285261/2000 proposes a copper alloy excellent in strength stability and softening resistance wherein the content of Fe is well within the range from 1.0 to 3.0% and also the volume fraction of the dispersoids of 0.05 to 10 μm in average particle diameter is 0.5 to 10%.

A copper alloy increasing the amount of the chemical compounds of smaller sizes is proposed. For example, JP-A No. 130755/1998 proposes a high-strength high-conductivity copper alloy containing Fe of 0.05 to 3.5% and P of 0.01 to. 1.0%, wherein the particles are classified as particles less than 0.02 μm in particle diameter (small particles) or particles 0.02 to 100 μm in particle diameter (large particles) and the ratio of the number of the small particles to that of the large particles is one or more. In addition, JP-A No. 324935/1998 proposes a high-strength high-softening resistance copper alloy containing Fe of 0.5 to 5% and P of 0.01 to 0.2%, wherein the ratio of large particles 100 Å or more in particle diameter to small particles less than 100 Å in particle diameter is in the range from 0.004 to 1.000.

Also JP-A No. 220594/1994 proposes a technology of improving strength and softening resistance by containing Fe of 0.01 to 0.3%, P of 0.005 to 0.4%, Zn of 1.5 to 5% and Sn of 0.2 to 2.5% and regulating the sizes of chemical compounds containing Fe and P so as not to coarsen in excess of 150 Å. In addition, JP-A No. 178670/2000 proposes a high-strength high-conductivity copper alloy containing Fe and P by 0.05 to 2% in total, Zn of 5 to 35% and Sn of 0.1 to 3%, wherein chemical compounds containing Fe and P of 0.2 μm or less in particle diameter disperse uniformly.

However, the aforementioned technologies of controlling the precipitation state of chemical compounds containing Fe and P (dispersoids) in a Cu—Fe—P alloy do not focus attention on the dispersoids of chemical compounds containing Fe and P of 20 nm or less in average particle diameter which are yet smaller than those regulated in those technologies.

It is true that there are some regulations containing dispersoids of chemical compounds containing Fe and P or the like having fine average particle diameter not exceeding 20 nm in some of the aforementioned documentary technologies. However, any of the technologies of controlling the precipitation state of such chemical compounds containing Fe and P does not regulate such a magnification of a TEM (transmission electron microscope) as to be able to observe dispersoids of chemical compounds containing Fe and P having fine average particle diameter not exceeding 20 nm. Even when a magnification is regulated, the magnification in the regulation is at most 10,000. With a TEM of 10,000 magnifications, such fine dispersoids cannot be observed. In order to comprehend the state (size and number) of dispersoids having fine average particle diameter not exceeding 20 nm quantitatively and accurately, it is necessary to make observation with a TEM of at least 100,000 magnifications.

Resultantly, the aforementioned documentary technologies do not substantially comprehend dispersoids themselves of chemical compounds containing Fe and P or the like having fine average particle diameter not exceeding 20 nm or do not substantially recognize the influence of the fine dispersoids on the properties of a copper alloy.

In addition, among the aforementioned documentary technologies, the content of Fe is as high as 0.5% or more in the cases of JP-A Nos. 285261/2002 and 324935/1998 and the contents of Zn and Sn are high in the cases of JP-A Nos. 220594/1994 and 178670/2000. Therefore, those technologies are common with the prior technologies of increasing the contents of Fe and P or adding a third element as explained above in order to increase strength. In this light, even though fine dispersoids are increased, an electric conductivity lowers inevitably.

Therefore, the simultaneous achievement of a higher strength and a higher conductivity has not been realized with the aforementioned conventional technologies and there have been rigid limitations in realizing a Cu—Fe—P alloy having a good balance between a higher conductivity and a higher strength or simultaneously having both the properties which are required along with the aforementioned trends of a larger capacity, a smaller size and higher integration of a semiconductor device.

SUMMARY OF THE INVENTION

The present invention has been established to solve such problems and the object thereof is to provide a Cu—Fe—P alloy simultaneously having both a higher strength and a higher conductivity.

As one preferred aspect, the gist of the present invention is that: a high-strength high-conductivity copper alloy contains Fe of 0.01 to 0.5% (in mass, and so forth) and P of 0.01 to 0.3% with the balance consisting of copper and unavoidable impurities; and, in the copper alloy, the mass content ratio of Fe to P, namely Fe/P, is in the range from 0.5 to 6.0 and the volume fraction and the number of dispersoids of 1 to 20 nm in average particle diameter in the microstructure of the copper alloy are 1.0% or more and 300 pieces/μm² or more, respectively.

In the present invention, a Cu—Fe—P alloy is arranged so as to contain dispersoids such as fine chemical compounds containing Fe and P of 20 nm or less in average particle diameter, whose effects and influences on the properties of the copper alloy have not hitherto been noticed or recognized, as much as possible in the copper alloy in accordance with the aforementioned regulations stipulated by the volume fraction and the number of the particles.

By so doing, with relatively small contents of Fe and P, a high-strength high-conductivity Cu—Fe—P alloy having an electric conductivity of not less than 80% IACS at the level of 140 to 150 Hv in hardness (480 to 530 MPa in tensile strength) or an electric conductivity of not less than 75% IACS even at the level of 160 Hv in hardness (570 MPa in tensile strength) can be provided.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Microstructure of Copper Alloy

The term “dispersoids” cited in the present invention means dispersoids whose average particle diameter is in the range from 1 to 20 nm when a microstructure of a copper alloy is observed with a transmission electron microscope of 100,000 magnifications. The main components of dispersoids are Fe—P chemical compounds and the dispersoids are mainly composed of chemical compounds containing Fe and P and the like formed by adding Fe, Cu—P chemical compounds and others to the main components.

Such fine dispersoids are newly formed during the production of a copper alloy, for example during annealing after cold rolling. That is, such fine dispersoids form a chemical compound phase precipitated finely from a copper matrix through annealing. Therefore, they are different from coarse dispersoids which form during casting and exist in the microstructure of the copper alloy from beginning. In this light, unless the microstructure of the copper alloy is observed with a transmission electron microscope of not less than 100,000 magnifications, such fine dispersoids cannot be observed.

The present invention stipulates that the volume fraction and the number of such fine dispersoids are 1.0% or more and 300 pieces/μm² or more, respectively. The pinning capability to suppress the transfer and extinction of dislocations of such fine dispersoids is, against all expectations, markedly larger than that of dispersoids coarser than those. Accordingly, by arranging a Cu—Fe—P alloy so as to contain dispersoids such as fine chemical compounds containing Fe and P of 20 nm or less in average particle diameter as much as possible in the microstructure of the copper alloy, the aforementioned pinning capability increases and thus a higher strength can be obtained.

The effect of lowering the electric conductivity of a copper alloy in the case of such fine dispersoids of 20 nm or less in average particle diameter is markedly less than that in the case of dispersoids coarser than those. Therefore, fine dispersoids can strengthen a copper alloy with less lowering of the electric conductivity of the copper alloy than dispersoids coarser than those.

The pinning capability of coarse dispersoids of over 20 nm in average particle diameter is low as stated above. For that reason, the present invention stipulates that the upper limit of the average particle diameter of dispersoids is 20 nm. On the other hand, in the case of dispersoids less than 1 nm in average particle diameter, they are hardly detected and measured even with a transmission electron microscope of 100,000 magnifications and moreover the pinning capability thereof lowers inversely. For that reason, the present invention stipulates that the lower limit of the average particle diameter of dispersoids is 1 nm.

When the volume fraction of such fine dispersoids is less than 1.0% or the number thereof is less than 300 pieces/μm², the number of particles to exhibit the effects is insufficient and thus a high strength of 140 to 150 Hv level in hardness (480 to 530 MPa level in tensile strength) cannot be obtained. Moreover, when the number of such fine dispersoids as stipulated in the present invention is small under a certain chemical composition, it is most likely that the rest of the dispersoids exist as coarser ones. As a result, the electric conductivity lowers and a high strength and a high conductivity satisfying an electric conductivity of not less than 80% IACS at the level of 140 to 150 Hv in hardness (480 to 530 MPa in tensile strength) or an electric conductivity of not less than 75% IACS even at the level of 160 Hv in hardness (570 MPa in tensile strength) cannot be attained.

Further, the present invention stipulates the amount of fine dispersoids of 1 to 20 nm in average particle diameter. However, as long as this stipulation is satisfied, it is acceptable that coarse dispersoids of over 20 nm in average particle diameter exist in the microstructure of the copper alloy in an appropriate amount within a range not to hinder the object of the present invention.

In the present invention, the diameter of dispersoids d is defined as the average of the maximum diameter of each dispersoid. In other words, the value obtained by averaging the diameter d of each dispersoid in a visual field observed with a transmission electron microscope of 100,000 magnifications is the average particle diameter referred to in the present invention. It is absolutely acceptable to further average the measurement results in plural visual fields.

In the same way, with regard to the number of dispersoids, the value obtained by averaging a measured number per μm² of each dispersoid in a visual field observed with a transmission electron microscope of 100,000 magnifications (images obtained by the observation are subjected to image analysis) is the number of dispersoids referred to in the present invention. It is absolutely acceptable to further average the measurement results in plural visual fields.

Likewise, with regard to the volume fraction of dispersoids in the present invention, the area percentage of dispersoids of 1 to 20 nm in average particle diameter in an area of 1 μm×1 μm (1 μm²) in a visual field observed with a transmission electron microscope of 100,000 magnifications is obtained and the obtained value is defined as the volume fraction of the dispersoids.

Chemical Composition of Copper Alloy

The reasons for specifying the chemical composition in a copper alloy according to the present invention are explained hereunder. With regard to a chemical composition, in order to attain a high strength and a high conductivity, a copper alloy according to the present invention is arranged so as to basically contain Fe of 0.01 to 0.5% and P of 0.01 to 0.3% in mass with the balance consisting of copper and unavoidable impurities, wherein the mass content ratio of Fe to P, namely Fe/P, is in the range from 0.5 to 6.0.

As described earlier, with the means of increasing the amounts of elements such as increasing the contents of Fe and P or adding a third element such as Sn, Mg, Ca or the like which has hitherto been adopted for increasing a strength, a strength increases but an electric conductivity deteriorates inevitably. A great advantage of the present invention is that, even though such a means as to increase the amounts of elements in order to increase strength is not adopted, a higher strength and a higher conductivity can be obtained by the aforementioned stipulation on fine dispersoids.

Note that, it is acceptable that a copper alloy according to the present invention further contains Zn of 0.005 to 0.5% and/or Sn of 0.001 to 0.5% as necessary within ranges not to hinder the higher strength and higher conductivity of the present invention.

Fe: 0.01 to 0.5%

Fe is an element necessary for increasing strength and softening resistance by precipitating as the fine dispersoids stipulated in the present invention in a copper alloy. When an Fe content is less than 0.01%, the fine dispersoids stipulated in the present invention are insufficient. For that reason, it is necessary that an Fe content is not less than 0.01% in order to effectively exhibit the effects on strengthening and the like. On the other hand, when Fe is contained in excess of 0.5%, a high conductivity is not secured. Further, if it is attempted to increase the amount of dispersoids in order to secure a high conductivity, the coarsening of precipitate particles is caused and inversely the fine dispersoids stipulated in the present invention become insufficient. As a result, strength lowers and the simultaneous achievement of a higher strength and a higher conductivity cannot be realized. For those reasons, an Fe content is determined to be in the range from 0.01 to 0.5 mass %.

P: 0.01 to 0.3%

P has an oxidation function and also is an element necessary for increasing strength and softening resistance of a copper alloy by forming dispersoids together with Fe. When a P content is less than 0.01%, the fine dispersoids stipulated in the present invention are insufficient. For that reason, it is necessary that a P content is not less than 0.01% in order to effectively exhibit the effects on strengthening and the like. On the other hand, when P is contained in excess of 0.3%, an electric conductivity deteriorates and a high conductivity is not secured. In addition, hot workability also deteriorates. For those reasons, a P content is determined to be in the range from 0.01 to 0.3 mass %.

Fe/P: 0.5 to 6.0

In order to precipitate an above-stipulated amount of the fine dispersoids stipulated in the present invention, the present invention stipulates not only the individual contents of Fe and P but also the mass content ratio of Fe to P, namely Fe/P. When the value of Fe/P is less than 0.5, P is contained in excess and dissolves in a copper matrix, and thus an electric conductivity deteriorates and a high conductivity is not secured. On the other hand, when the value of Fe/P exceeds 6.0, inversely Fe is contained in excess and grows as coarse simple Fe particles and resultantly a strength lowers. For those reasons, the value of Fe/P is determined to be in the range from 0.5 to 6.0.

Zn: 0.005 to 0.5%

Zn is an element effective in improving thermal abrasion resistance of Sn plating or soldering used for the joints of electronic components and suppressing thermal abrasion. It is preferable to contain Zn by not less than 0.005% in order to exhibit such an effect effectively. However, when Zn is contained in excess of 0.5%, not only the wet-spreadability of molten Sn or solder rather deteriorates but also an electric conductivity deteriorates considerably. For those reasons, Zn is contained selectively in the range from 0.005 to 0.5 mass %.

Sn: 0.001 to 0.5%

Sn contributes to the increment of the strength of a copper alloy. It is preferable to contain Sn by not less than 0.001% in order to exhibit such an effect effectively. However, when Sn is contained in excess of 0.5%, the effect is saturated and an electric conductivity deteriorates considerably. For those reasons, Sn is contained selectively in the range from 0.001 to 0.5 mass %.

Other elements, for example Al, Cr, Ti, Be, V, Nb, Mo, W, Mg, Ni, etc., are impurities and facilitate not only the formation of coarse dispersoids but also the deterioration of an electric conductivity. For that reason, it is preferable to lower the content as low as possible in the range not exceeding 0.5 mass % in total. Other elements, such as B, C, Na, S, Ca, As, Se, Cd, In, Sb, Pb, Bi, MM (misch metal), etc., contained in a copper alloy in minute amounts also facilitate the deterioration of an electric conductivity. For that reason, it is preferable to lower the content as low as possible in the range not exceeding 0.1 mass % in total.

Production Method

Next, preferable production conditions for making the microstructure of the copper alloy into a structure stipulated in the present invention are explained hereunder. It is not necessary to largely change the production process itself in the production of a copper alloy according to the present invention and an ordinary production process can be employed for the production. That is, molten copper alloy whose chemical composition is adjusted as described above is cast. Then, the surface of the cast ingot is ground, thereafter the cast ingot is hot rolled after subjected to heat treatment or soaking, and the plate after hot rolled is cooled with water. Thereafter, the plate is subjected to primary cold rolling called intermediate rolling, then to annealing, cleaning and thereafter finishing (final) cold rolling, and resultantly produced into the copper alloy plate or the like of a product thickness.

In the production process, it is effective to apply annealing under the following conditions at the production in order to control the production process so as to form the dispersoid structure wherein the volume fraction and the number of dispersoids of 1 to 20 nm in average particle diameter are 1.0% or more and 300 pieces/μm² or more, respectively, as described above.

That is, as described earlier, the fine dispersoids stipulated in the present invention form a chemical compound phase finely precipitated newly from a copper matrix through annealing. In order to precipitate such fine dispersoids, annealing is applied after primary cold rolling in the production process of the copper alloy.

Here, if it is intended to obtain a high conductivity only through one time annealing, it is essential to raise the annealing temperature. If an annealing temperature is raised, the amount of dispersoids increases and that causes the growth and coarsening of the dispersoids. In this light, it is preferable to control the annealing process so as to form the dispersoid structure composed of the fine dispersoids as mentioned above by: applying annealing divided into several times; controlling an annealing temperature per one time annealing to 430° C. or lower; thus obtaining a high conductivity; and suppressing the growth and coarsening of the dispersoids.

Further, when cold rolling is applied between annealing and subsequent annealing, the cold rolling causes lattice defects to increase, the lattice defects act as precipitation nuclei at the subsequent annealing and therefore the dispersoid structure composed of the fine dispersoids as mentioned above is likely to be obtained.

Therefore, in view of the above conditions, such a process as to repeatedly apply cold rolling and annealing twice for each between the end of hot rolling and the finishing (final) cold rolling in the production process of a copper alloy is preferable because such a dispersoid structure composed of the fine dispersoids as mentioned above is likely to be obtained.

The hold time at the maximum temperature in annealing is determined to be in the range from 0.5 to 20 hours. When a hold time is shorter than 0.5 hour, the amount of precipitates is insufficient and an electric conductivity does not improve. In contrast, when a hold time exceeds 20 hours, even at a temperature of 430° C. or lower, precipitate particles grow and coarsen.

EXAMPLES

Examples according to the present invention are explained hereunder. Copper alloy plates were produced by casting copper alloys having various compositions shown in Table 1 below and the properties thereof were evaluated. Here, in the copper alloy plates having various compositions shown in Table 1, the total amount of Al, Cr, Ti, Be, V, Nb, Mo, W, Mg, Ni, etc. as elements other than the elements shown in Table 1 was not more than 0.5 mass %. Further, the total amount of B, C, Na, S, Ca, As, Se, Cd, In, Sb, Pb, Bi, MM (misch metal), etc. slightly contained in the copper alloys as elements still other than the above elements was not more than 0.1 mass %.

The concrete production method of copper alloy plates is as follows. Copper alloys were melted and refined in a coreless furnace and thereafter cast by the semi-continuous casting method, and thus ingots 70 mm in thickness, 200 mm in width and 500 mm in length were produced. Then, the surface of each of the ingots was ground and the ingots were heated and thereafter hot rolled into the thickness of 16 mm at a temperature of 950° C. The surface of each of the hot-rolled plates was ground again to remove oxide scales and thereafter each hot-rolled plate was subjected to cold rolling and annealing repeatedly for predetermined times within the range from one to three times (the number of times of cold rolling was identical to that of annealing) as the number of times of annealing for each example is shown in Table 1. Thereafter, the copper alloy plates were subjected to the final cold rolling and the copper alloy plates 0.2 mm in thickness were produced. The highest annealing temperature among the temperatures in the repetition of annealing was defined as the maximum annealing temperature and the maximum annealing temperature is shown in Table 1 for each example.

Test pieces were cut out from the copper alloy plates of all examples thus produced and subjected to the measurement of the volume fraction (%) and the number of the fine dispersoids by the observation of each structure, tensile test, hardness measurement and electric conductivity measurement. The results are shown in Table 1.

In the observation of a structure, the volume fraction and the number of dispersoids of 1 to 20 nm in average particle diameter at the time when the microstructure of the copper alloy was observed with a transmission electron microscope of 100,000 magnifications were measured by the aforementioned measurement method.

A tensile test was applied to a JIS #13 test piece produced by cutting it out in a direction parallel with the rolling direction. Hardness was measured with a micro-Vickers hardness tester while a load of 0.5 kg was applied.

An electric conductivity was obtained by: forming a rectangular test piece 10 mm in width and 300 mm in length through milling; measuring an electric resistance with a double-bridge type resistance measuring device; and then calculating by the average cross section method.

As it is obvious from Table 1, in the case of the invention examples 1 to 9, each copper alloy plate contained Fe of 0.01 to 0.5% and P of 0.01 to 0.3% wherein the value of Fe/P was in the range from 0.5 to 6.0, those values being well within the composition range of a copper alloy according to the present invention, and also selectively contained Zn and Sn in stipulated ranges respectively. Further, with regard to the production method, the copper alloy plates were produced under preferable annealing conditions.

Resultantly, in the cases of the invention examples 1 to 9, the volume fraction and the number of dispersoids of 1 to 20 nm in average particle diameter were 1.0% or more and 300 pieces/μm² or more, respectively, when each microstructure of the copper alloy was observed with a transmission electron microscope of 100,000 magnifications.

As a result, each of the copper alloy plates obtained an electric conductivity of 83 to 80% IACS at the level of 144 to 157 Hv in hardness (503 to 552 MPa in tensile strength) or an electric conductivity of 86 to 82% IACS even at the level of 161 to 165 Hv in hardness (570 to 581 MPa in tensile strength) and thus had a high strength and a high conductivity.

In contrast, as it is obvious from Table 1, in the case of the comparative example 10, the Fe content in the copper alloy was 0.007% and lower than the lower limit. Resultantly, though the annealing was applied under preferable conditions, the volume fraction of the fine dispersoids was 0.8% and lower than the lower limit, and thus all of the hardness, tensile strength and electric conductivity were low.

In the case of the comparative example 11, the annealing was applied under preferable conditions and also the volume fraction and the number of the fine dispersoids were well within the ranges stipulated in the present invention. However, the Fe content in the copper alloy was 0.66% and exceeded the upper limit, and therefore the electric conductivity was extremely low and thus the simultaneous achievement of a higher strength and a higher conductivity was not realized.

In the case of the comparative example 12, the P content in the copper alloy was 0.008% and lower than the lower limit. Resultantly, though the annealing was applied under preferable conditions, the volume fraction of the fine dispersoids was 0.9% and lower than the lower limit, and thus all of the hardness, tensile strength and electric conductivity were low.

In the case of the comparative example 13, the annealing was applied under preferable conditions and also the volume fraction and the number of the fine dispersoids were well within the ranges stipulated in the present invention. However, the P content in the copper alloy was 0.33% and exceeded the upper limit, and therefore the electric conductivity was extremely low and thus the simultaneous achievement of a higher strength and a higher conductivity was not realized.

In the case of the comparative example 14, though the contents of Fe and P in the copper alloy were well within the ranges stipulated in the present invention, the value of Fe/P was 0.31 and lower than the lower limit. As a result, though the annealing was applied under preferable conditions and also the volume fraction and the number of the fine dispersoids were well within the ranges stipulated in the present invention, the electric conductivity was considerably low in comparison with the hardness and tensile strength.

In the case of the comparative example 15, though the contents of Fe and P in the copper alloy were well within the ranges stipulated in the present invention, the value of Fe/P was 6.50 and exceeded the upper limit. For that reason, though the annealing was applied under preferable conditions, the number of the fine dispersoids was 250 pieces/M² and lower than the lower limit. As a result, all of the hardness, tensile strength and electric conductivity were considerably low.

In the case of the comparative example 16, the annealing was applied under preferable conditions and also the volume fraction and the number of the fine dispersoids were well within the ranges stipulated in the present invention. However, the Zn content in the copper alloy was 1.2% and exceeded the upper limit, and resultantly the electric conductivity was considerably low in comparison with the hardness and thus the simultaneous achievement of a higher strength and a higher conductivity was not realized. Further, since the Zn content was high, there was a possibility of poor soldering.

In the case of the comparative example 17, the annealing was applied under preferable conditions and also the volume fraction and the number of the fine dispersoids were well within the ranges stipulated in the present invention. However, the Sn content in the copper alloy was 0.9% and exceeded the upper limit, and resultantly the electric conductivity was considerably low in comparison with the hardness and tensile strength and thus the simultaneous achievement of a higher strength and a higher conductivity was not realized.

In the case of the comparative example 18, though the composition of the copper alloy was within the ranges stipulated in the present invention, the maximum annealing temperature was 500° C. and exceeded the preferable upper limit, the volume fraction of the fine dispersoids was 1.8% and close to the lower limit, and moreover the number thereof was 200 pieces/μm² and lower than the lower limit. As a result, both the hardness and electric conductivity were considerably low.

In the case of the comparative example 19, though the composition of the copper alloy was within the ranges stipulated in the present invention likewise, the annealing was applied only once and plural times of annealing was not applied, and also the number of the fine dispersoids was 150 pieces/μm² and lower than the lower limit. As a result, all of the hardness, tensile strength and electric conductivity were considerably low.

In the case of the comparative example 20, though the composition was identical to that of the invention example 1 and was within the ranges stipulated in the present invention likewise, the hold time at the maximum annealing temperature was 0.2 hour and lower than the preferable lower limit, and the volume fraction and the number of the fine dispersoids were 0.6% and 250 pieces/μm², respectively, and both were lower than the lower limits. As a result, the electric conductivity was considerably lower than that of the invention example 1.

In the case of the comparative example 21, though the composition was identical to that of the invention example 5 and was within the ranges stipulated in the present invention likewise, the hold time at the maximum annealing temperature was 30 hours and exceeded the preferable upper limit, and the number of the fine dispersoids was 280 pieces/μm² and lower than the lower limit. As a result, the hardness and tensile strength were inferior to the invention example 5.

In the case of the comparative example 22, though the composition was identical to that of the invention example 9 and was within the ranges stipulated in the present invention likewise, the maximum annealing temperature was 460° C. and exceeded the preferable upper limit and, the number of the fine dispersoids was 230 pieces/μm² and lower than the lower limit. As a result, the hardness and tensile strength were inferior to the invention example 9.

The above results ensure the critical significance of the chemical composition, structure, preferable annealing conditions and the like in a copper alloy plate according to the present invention in order to secure a higher strength and a higher conductivity.

[Table 1]

As explained above, the present invention makes it possible to provide a copper alloy that can meet the requirements of a higher strength and a higher conductivity, which requirements arise with the cross-sectional area of an IC lead frame being reduced. Further, the present invention makes it possible to attain a higher strength and a higher conductivity of a copper alloy used for not only IC lead frames but also other electric conductive components such as connectors, terminals, switches, relays, etc. in electric and electronic components.

The foregoing invention has been described in terms of preferred embodiments. However, those skilled, in the art will recognize that many variations of such embodiments exist. Such variations are intended to be within the scope of the present invention and the appended claims. TABLE 1 Number of Characteristics of annealing Maximum Grain final product Chemical components applied between annealing Annealing volume Number of Hard- Tensile Conduc- (mass %) hot rolling and tempera- retention percentage grains ness strength tivity No. Fe P Fe/P Zn Sn final cold rolling ture (° C.) time (hr) (%) (pieces/μm²) (Hv) (Mpa) (% IACS) Inven- 1 0.16 0.05 3.20 — — 2 410 5 5.0 1000 155 545 89 tion 2 0.11 0.04 2.75 — — 2 380 8 3.7 1200 149 524 88 exam- 3 0.05 0.04 1.25 — — 2 350 10 2.6 1400 144 503 83 ples 4 0.45 0.24 1.88 — — 2 430 6 7.7 800 162 572 79 5 0.38 0.08 4.75 0.03 — 2 420 7 6.0 900 157 552 80 6 0.10 0.03 3.33 0.2 — 2 380 14 4.2 1250 153 540 85 7 0.28 0.11 2.55 0.05 0.01 2 400 10 5.9 1050 165 581 82 8 0.12 0.04 3.00 0.3 0.3 2 390 2 4.4 1200 163 575 75 9 0.17 0.06 2.83 0.01 0.03 3 370 18 5.2 1300 161 570 86 Com- 10 0.007 0.01 0.70 — — 2 340 5 0.8 1000 132 453 76 para- 11 0.66 0.19 3.47 — — 2 430 10 9.1 700 148 519 65 tive 12 0.02 0.008 2.50 — — 2 360 5 0.9 900 133 457 75 exam- 13 0.48 0.33 1.45 — — 2 420 12 8.8 750 149 522 61 ples 14 0.14 0.45 0.31 — — 2 400 8 4.7 1050 151 533 56 15 0.13 0.02 6.50 — — 2 390 10 3.5 250 129 440 70 16 0.20 0.06 3.33 1.2 — 2 400 7 5.6 1150 157 549 62 17 0.33 0.14 2.36 — 0.9 2 420 5 7.0 1000 166 582 58 18 0.06 0.02 3.00 0.03 — 2 500 2 1.8 200 125 424 88 19 0.08 0.03 2.67 0.01 0.01 1 480 3 4.5 150 122 409 87 20 0.16 0.05 3.20 — — 2 410 0.2 0.6 250 159 565 68 21 0.38 0.08 4.75 0.03 — 2 400 30 6.8 280 148 520 82 22 0.17 0.06 2.83 0.01 0.03 2 460 5 5.3 230 143 499 87 

1. A high-strength high-conductivity copper alloy containing Fe of 0.01 to 0.5 mass % and P of-0.01 to 0.3 mass % with the balance consisting of copper and unavoidable impurities, wherein the mass content ratio of Fe to P, namely Fe/P, is in the range from 0.5 to 6.0 and the volume fraction and the number of dispersoids of 1 to 20 nm in average particle diameter in the microstructure of the copper alloy are 1.0% or more and 300 pieces/μm² or more, respectively.
 2. The copper alloy according to claim 1, further containing Zn of 0.005 to 0.5 mass %.
 3. The copper alloy according to claim 1, further containing Sn of 0.001 to 0.5 mass %. 